Selective tobacco smoke filter



United States Patent 3,003,504 SELECTIVE TOBACCO SMOKE FILTER George P.Touey and John E. Kiefer, Kingsport, Tenn., assignors to Eastman KodakCompany, Rochester, N.Y.,

a corporation of New Jersey No Drawing. Filed Feb. 5, 1959, Ser. No.791,283 6 Claims. (Cl. 131-208) This invention relates to a tobaccosmoke filter. More ters will be further discussed below. A wide varietyof materials have been suggested in the prior art as filters for tobaccosmoke. Thus, such products as cotton, paper, asbestos, regeneratedcellulose and certain synthetic fibers have been disclosed as filtermedia for tars and nicotine of cigarette, pipe and cigar smoke.

Although materials as aforesaid remove a certain pro portion of theparticulate, or liquid-solid phase of tobacco smoke, such as the highboiling tar and nicotine particles, these materials are of little valuein removing the constituents in the gaseous phase of the smoke. It isknown that, although some of the gaseous constituents of tobacco smokeare desirable from the standpoint of taste, flavor and aroma, others areundesirable and are quite irritating to the smokers throat and lungs.Many of the major irritating gases in tobacco smoke are low molecularweight aldehydes. In particular, acetaldehyde, a Well-known irritant, isalways present in cigarette smoke in significantamounts.

In order to remove such vapors from cigarette smoke, various adsorbentshave been suggested in such prior filters. Thus, materials as activatedsilica gel, activated aluminum oxide and the diatomaceous earths havebeen used. Such products, however, have several undesirable features.One disadvantage is the fact that, on storage in the presence oftobacco, they adsorb moisture. and tobacco flavors and odors. This notonly impairs the quality of the cigarette but also deactivates theadsorbent rendering it incapable of removing aldehyde vapors. Also,

the adsorbents are not selective for the irritating aldehydes but alsoremove other gaseous constituents which are desirable. In addition,filters of these adsorbents may be harsh and irritating to the smokerstongue and, from an economical standpoint, they cannot be readilyprepared on standard filter making equipment.

It is believed apparent, therefore, that the development of a filterwhich is somewhat selective in its removal action, and which inparticular removes the undesired aldehydic components represents ahighly desirable 'result. We have now found that-it is possible toselectively remove a substantial portion of the irritating aldehydevapors from cigarette smoke by employing a filament filter containing afinely divided polymer of a certain type uniformly spread over thesurface of the filaments in the filter.

One .object of the invention, therefore, is to provide a filament typeof tobacco smoke filter which will remove a substantial portion of theparticulate (liquid-solid) phase of tobacco smoke by physical means suchas adsorption or impingement, and which, in addition, will chemically orotherwise remove acetaldehyde and other aldehyde vapors present in thesmoke. Another object is to provide a filter which will selectivelyremove the undesirable the chloromethylated product is treated withammonia aldehyde vapors without removing certain vapors or 'ice aromasthat contribute to the enjoyment of smoking. A

further object is to provide a filter which will remain effective forthe removal of the aldehyde vapors even after prolonged exposure tomoisture vapor or tobacco odors as would normally be encountered in asealed package of cigarettes. Still another object is to providesuitable methods for manufacturing filters of the class referred to.Other objects will appear hereinafter.

We have found that there are certain polymeric compounds, namelyinsoluble polymeric amine powders, which polymeric compounds havefunctional amino groups therein that will remove the undesired aldehydesfrom cigarette smoke and yet not materially adversely affect the aroma,taste and the properties of the smoke either during storage of thefilter cigarettes or during the smoking thereof. The reaction of suchpolymers with the aldehydes may be illustrated by the followingequations wherein R represents the polymer nucleus.

The particular types of insoluble polymers which have been found to bemost effective in the removal of the aldehydes from the gaseous phase ofcigarette smoke are those containing primary and secondary amine groupsin their free amine form as generally illustrated in the above formulas.

The preferred polymer, which would be employed in powered form, aswillbe explained hereinafter consists of a polystyrene polymer cross-linkedwith divinyl benzene and which contains aliphatic primary and secondaryamine groups attached to its benzene rings. The number ofamine-containing substituent groups can vary between an average of 0.7and 1.5 for each benzene ring in the polymer. The amount of divinylbenzene constituent in the cross-linked polymer can vary between ,2 and15%.

In FIG. 1 is shown the formula for the insoluble polymeric amine powderwhich we have found to be highly effective in combining with thealdehyde gases of cigarette smoke.

FIGURE 1 -CH-CH2CH-CH: CHCHT r i i OHINR CHzNR CHzNR where i H R=H, CH,C nHum-n, (CH1) n[N(C l) n] mNHI The insoluble polymeric amines of thisinvention may be prepared by known procedures which involve a threestepprocess. The first step consists of the preparation of thestyrene-divinyl benzene cross-linked polymer by the polymerization ofstyrene in the presence of 2-15% divinyl benzene, based on the totalmonomer weight. After the cross-linked polymer is prepared it is thenchloromethylated by conventional procedures. Finally,

or a monoamine.

It is by this last reaction that the alkylamino groups are incorporatedinto the polymer structure:

(HCI+EGHO) CHM NH,

secondary amine group on one benzene unit with a residual chloromethylgroup on an adjacent benzene unit. This is shown by the followingequation:

A wide variety of primary alkylamines can be used to react with thechloromethylated cross-linked polymer to give the desired product.Examples of such amines are methylamine, ethylamine, propylamine,isopropylamine, butylamine, isobutylamine, cyclohexylarnine,ethylenediamine, tetraethylenediamine, diethylenetetraamine anddiethylenetriamine. It is also understood that the amine can carryadditional substituent groups on their alkyl components such ashydroxyl, amido, methoxy and the like. Thus, the primary alkanol aminessuch as ethanolamine can be usedv to react with the chloromethylgroupson the styrene-divinyl benzene polymer.

The size of the insoluble polymeric material above described is also animportant part of this invention. In order to incorporate the powderinto the finished filament filter it has been found that the productshould be ground to the point where it can pass through a 100 meshscreen or finer. In this condition it can be readily dusted onto thesurface of the spread out filaments of cellulose acetate prior to thefabrication of the filter. It is also desirable to spray the spread-outfilaments with a cellulose ester type of organic plasticizer eitherbefore or after it is dusted with the p wder. The plasticizer functionsas a curing or bonding agent for the filter by partially solvatgig thecellulose filaments at random spots within the ter.

4 Satisfactory plasticizers for this purpose are glycerol diacetate,glycerol triacetate, glycerol dipropionate, gly- C HzNHa i CHnNR l CHnN0 H2) nNH:

cerol tripropionate, propylene glycol monoand diacetate,di(methoxyethyl)phthalate, methylphthalylethyl glycollate and triethylcitrate. Aside from forming a firm or rigid filter, the plasticizer aidsin bonding the above described polymer powder to the filaments. This isbecause the powder becomes partially embedded in the filaments after theplasticizer has softened their surface.

A very desirable form of the insoluble amino polymer is a powder whichwill pass through a 200 mesh screen or finer. This is because such apowder can be suspended in the plasticizer used as the hardening agentfor the filter and sprayed on the filaments rather than being dustedthereon. This simplifies the operation somewhat by eliminating a dustingbooth or other suitable dusting apparatus in the fabrication of thefilter. If desired, the plasticizer or hardening agent can be dilutedwith a solvent prior to the addition of the powder if the suspension orslurry technique is to be used for applying the powder. Suitablesolvents which can be used as diluents for the plasticizer are thealkylene glycols and glycerine. In those cases where the plasticizer orfilter hardening agent is water-miscible such as glycerol diacetate,propylene glycol acetate, etc., the plasticizer may be diluted withwater.

The amount of the powdered polymer which we prefer to add to thefinished filter will vary with the number of primary and secondary aminogroups in its structure and the amount of aldehydes which one desires toremove from the cigarette smoke. When the polymer contains a nitrogencontent of within the range of 5 to 15%, the amount of powdered additiverequired will be within the range of 530%. This percentage value isbased on the weight of the combination of cellulose acetate fila-.

ments and powder only and does not include the weight of the plasticizer(or plasticizer and diluent) and paper wrapper. On this basis when 5%powder (nitrogen content 5%) is added to the filter, the filter willremove at least 5% of the gaseous aldehydes calculated as acetaldehyde.When 30% of the powder (nitrogen content 9l0%) is added, the filter willremove up to 60% of the gaseous aldehydes.

A method for determining if a cigarette filter removes gaseous aldehydeshas been developed and published:

Gaseous Phase of Cigarette Smoke-Isolation and Analysis for TotalAldehydes, G. P. Touey, Anal. Chem. 27, 1788- (1955).

Another advantage of using the insoluble amine polymer in a finelydivided form is that when properly applied to the tow filaments it alsoaids in removing the tar and nicotine particles in the particulate phaseof cigarette smoke. This is because the particles are deposited on thefilaments and function as protrusions or humps. These protrusions extendinto the spaces between the filaments in a cellulose acetatefilament-type filter. Part of the nico-.

tine and tar particles, therefore, which might normally ances or thenumber of filaments present in the filter will range.

from 5,000 to 10,000. When the finest denier per filament is used (0.6d./f.) the number of filaments present in the filter will range from30,000 to 40,000.

The number of crimps in the cellulose acetate tow can range from 8 to 25crimps per inch. The more desirable number of crimps will range from12-18.

For a still further understanding of our invention, reference may bemade to the following eXamples which illustrate certain of our preferredembodiments.

EXAMPLE I A length of cellulose acetate crimped tow of denier perfilament and containing 17,000 filaments was bloomed out with an air jetdevice to a width of inches. While in this spread out condition the towwas sprayed on both sides with a plasticizer-type bonding agent(glycerol triacetate). It was then dusted on both sides with a powderconsisting of a styrene-divinyl benzene copolymer containing primary andsecondary alkylamine groups chemically bound to its benzene units. Thenitrogen content of the polymer was 9.8% and it had been ground until itwas capable of passing through a 200 mesh screen. After the spraying anddusting operation the tow was pulled back together into the form of acord and pulled through a cigarette filter rod making device whichconverted it to paper-wrapped cylindrical rods 90 mm.in length and thecircumference of a king size cigarette. These rods were cut into filtertips 15 mm. in length; Analyses of the rods disclosed that theyconsisted of 70% cellulose acetate filaments, 15% plasticizer and 15polymeric amine powder, based on the weight of the combination withoutthe paper. Microscopic observation of a few of the opened rods revealedthat the powder was uniformly distributed on the filaments in the tow.

Ten of these filters were attached to commercial king size cigaretteswhich had been shortened by 15 mm. 'to compensate for the length of thefilter tips. These cigarettes were smoked to 30-mrn. butt lengths on anautomatic smoking apparatus designed for determining the tar andnicotine content of the smoke as well as the aldehyde content of thegaseous phase of the smoke.

The equipment and method have been described in An alytical Chemistry,vol 27, pp. 1788-90 (1955). The smoke was pulled by each pulf through anabsolute filter unit, followed by two gas absorption flasks containing adilute aqueous solution of dimedon, a Specific reagent for aldehydes. Aseach cigarette was smoked, the absolute filter removed all of nicotineand tars not removed by the filter tip while the dimedon solutionscrubbed the smoke gases free of aldehydes. By analyzing the material onthe absolute filter after the smoking test (10 cigarettes) it waspossible to determine how much tar and nicotine came through thecigarettes. By analyzing the contents of the absorption flasks it waspossible to determine how much of the low molecular weight aldehydes(calculated as acetaldehyde) were produced by the cigarettes. Finally,by smoking another set (10) of the same cigarettes, 35 mm. in length,and unfiltered, in the same manner it was possible to determine how muchnicotine, tar and gaseous aldehydes were produced by the cigarettewithout a filter. The results g in Table 1.

Table 1 v Mg. Mg. Cigarette Mg. Tar Nicotine Alde- Pressure Type ofFilter on Cigarette from 10 from 10 hydes Drop 1 Cigarettes Cigarettesfrom 10 (Average Cigarettes of 10) Cellulose acetate tow containing thecross-linked polyarnine powder 305 21 7.0 4. 0 Cellulose acetate toweontroL 360 23. 5 11. 2 3. 8 N0 filter 400 28.0 11.5 3. 1

of these two tests are listed in Table 1.

Control filters (15 mm.) without the cross-linked poly meric aminepolymer but containing 15% glycerol triacetate were also prepared fromanother length of the" tow and converted into 15-mm. filters in themanner described. These filters were attached to another setof the samebrand of king size cigarettes (mentioned above) which had been shortenedby 15 mm. This set,

were determined. The results of this test are also listed 1 Pressuredrop expressed in inches of water at an air flow rate of 17.5 ml. persecond through the cigarette.

The results in the table above show that the control filter removed 15%more tar and 16% more nicotine than the 15-mm. length of tobacco whichit replaced. However, it was no better than the tobacco (15 mm.) inremoving the gaseous aldehydes. The filter containing the cross-linkedpolystyrene powder removed 24% more tar, 25% more nicotine, and 37% morealdehydes than the 15 mm. length of tobacco it replaced.

EXAMPLE II A length of cellulose acetate crimped tow of 2.1 denier" perfilament and containing 26,000 filaments was bloomed I out to a width of10 inches. It was then sprayed on both sides with a suspensionconsisting of 30 parts cross-linked polymer powder-containing reactiveamino groups, 35 parts propylene glycol and 35 parts glyceroltriacetate. The polymer powder was a finely ground styrene-divinylbenzene copolymer containing primary and second ary alkylamine groupschemically bound to its benzene units. Its nitrogen content was 8.3% andthe average size of its particles was 8 microns.

After being sprayed with this slurry the tow was pulled back togetherinto the form of a cord and converted into 15-mm. filter tips asdescribed in Example I. Analysis of the tips disclosed that theyconsisted of 67% cellulose acetate, 11.5% glycerol triacetate, 11.5%propylene glycol and 10% powder, based on the weight of the combinationwithout the paper. Microscopic observation of a few of the openedfilters revealed that the powder was uniformly distributed on thefilaments. Ten of the filters were attached to commercial king sizecigarettes (same brand as used for Example I) which had been shortenedby 15 mm. These cigarettes were smoked on the smoking apparatus (ExampleI) to 30-min. butt lengths and the amounts of nicotine, tar and gaseousaldehydes (calculated as acetaldehyde) delivered by the cigarettes weredetermined (Table 2).

Control filters (15 mm.) which had been sprayed with a 50/50 (by weight)glycerol triacetate-propylene glycol solution containing nopolymerpowder were also prepared from the same 2.1 d./-f. tow. These filterscontained 15% glycerol triacetate, 15 propylene glycol and 70% celluloseacetate, based on the weight of the combination without the paper. Tenof the filters were attached to the king size cigarettes (same asExample I) which had been shortened by 15 mm. These cigarettes weresmoked on the smoking apparatus (Example I) to 30-min. butt lengths andthe amounts of nicotine, tar and gaseous aldehydes delivered weredetermined. (Table 2.)

, Table 2 Mg. Mg. Cigarette Mg. Tar Nicotine Alde- Pressure Type ofFilter on Cigarette from 10 from 10 hydes Drop Cigarettes Cigarettesfrom 10 Cigarettes Cellulose acetate tow containing cross-linked aminepowder 270 20 8. 4. 2 Cellulose acetate tow control- 307 22 11. 2 4.0

When these results are compared with those obtained from the unfilteredcigarette of Example I it is found that only the filter with thecross-linked amine powder removed aldehydes (26%). Also, the filtercontaining the powder removed 32% more tar and 29% more nicotine thanthe l5-rnm. length of tobacco it replaced. The control filter removed23% more tar and 22% more nicotine than the 15-mm. length of tobacco itreplaced.

It is believed apparent from the foregoing that we have shown animproved tobacco smoke filter that is especially useful in removingundesired aldehyde components from tobacco smoke.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. A tobacco smoke filter adapted to remove undesirable aldehydecomponents from tobacco smoke comprising an elongated filter bodyportion which is made up of several thousand longitudinally orientedsynthetic filaments, the filaments being encircled about theircircumference by a wrapper, the filter being characterized in that thefilaments carry on their surface a, substantial content of a polymericpowder material that has amine groups in its molecule, said polymercomposition being in accordance with the following general formula:

CHaNR CHzNR CHRNR 2. A filter in accordance with claim 1 wherein thefilaments are essentially comprised of cellulose acetate which containsplasticizer.

3. A filter in accordance with claim 1 wherein the filaments are crimpedcontinuous cellulose acetate filaments of a denier per filament of lessthan 16.

4. A filter adapted for removing aldehyde components from tobacco smokecomprised of a bundle of several thousand cellulose ester filaments, acontent of plasticizer, at least 10% by weight of the filaments,contained in the cellulose ester, and a content of styrene-divinylbenzene copolymer which contains primary and secondary alkyl aminegroups chemically bound to the benzene units of the copolymer carried onthe surface of said filaments in finely divided form.

5. A product in accordance with claim. 4 wherein the plasticizer is fromthe group consisting of glycerol diacetate, glycerol triacetate,glycerol dipropionate, glycerol tripropionate, propylene glycol monoanddiacetate, di (methoxyethyl)phthalate, methylphthalylethyl glycollateand triethyl citrate.

6. The product of claim 4 wherein the amount of powdered copolymer is530% by weight of the filaments.

References Cited in the file of this patent UNITED STATES PATENTS2,371,357 Schindler Mar. 13, 1945 2,577,843 Crosby et al. Dec. 11, 19512,774,680 Hackney et a1 Dec. 18, 1956 2,780,228 Touey Feb. 5, 19572,805,671 Hackney et a1 Sept. 10, 1957 2,815,760 Schreus et al Dec. 10,1957

1. A TOBACCO SMOKE FILTER ADAPTED TO REMOVE UNDESIRABLE ALDEHYDECOMPONENTS FROM TOBACCO SMOKE COMPRISING AN ELONGATED FILTER BODYPORTION WHICH IS MADE UP OF SEVERAL THOUSAND LONGITUDINALLY ORIENTEDSYNTHETIC FILAMENTS, THE FILAMENTS BEING ENCIRCLED ABOUT THEIRCIRCUMFERENCE BY A WRAPPER, THE FILTER BEING CHARACTERIZED IN THAT THEFILAMENTS CARRY ON THEIR SURFACE A SUBSTANTIAL CONTENT OF A POLYMERICPOWDER MATERIAL THAT HAS AMINE GROUPS IN ITS MOLECULE, SAID POLYMERCOMPOSITION BEING IN ACCORDANCE WITH THE FOLLOWING GENERAL FORMULA: